This invention relates to a method and apparatus for inspecting the thickness of blow molded containers.
The thickness of blow molded containers has previously been statistically sampled by removing a certain small percentage of containers from a production line. With modern blow molding equipment capable of producing over 400 containers per minute, such sampling will account for less than 0.1 percent of the entire production run.
One object of the present invention is to provide an improved method for inspecting blow molded containers.
In carrying out the above object, the method for inspecting blow molded containers is performed by conveying rotatively oriented and upstanding blow molded containers on a rotary wheel along a path of conveyance and directing a laser beam upwardly from the exterior of the conveyed containers toward the exteriors of the container bottoms so the laser beam impinges along a predetermined path on each container and is reflected downwardly at both an outer surface and at an inner surface of the container bottom. The method also involves detecting the reflected laser beam from the outer and inner surfaces of the container to determine the thickness of the container between its outer and inner surfaces along the predetermined path. The wheel is relatively driven at a constant speed of rotation so the laser detection measures the container bottom thickness along the same path on each container. Furthermore, the method involves removing from the conveyor each container having a thickness that is out of tolerance with respect to a design specification.
The blow molded container inspection method described above allows inspection of up to 100 percent of the containers such that any containers that do not have thicknesses within the design specification can be removed from the others.
In the preferred method disclosed, the laser beam is directed upwardly to measure the thickness along a predetermined path along a bottom of each container. Furthermore, the blow molded containers are cyclically positioned in an outstanding manner on a wheel of the conveyor in an oriented manner just after being blow molded, and the wheel is rotatively driven at a constant speed of rotation so the laser detection measures the container bottom thickness along the same path on each container.
Another object of the present invention is to provide improved apparatus for inspecting blow molded containers.
In carrying out the immediately preceding object, the blow molded container inspection apparatus includes a conveyor for conveying blow molded containers. A laser source of the apparatus directs a laser beam upwardly from the exterior of rotatively oriented and upright containers conveyed on a rotary wheel toward the container bottoms so the laser beam impinges along a predetermined path along each container bottom and is reflected downwardly from both outer and inner surfaces of the container bottom. A detector of the apparatus detects the laser beam reflected downwardly from the outer and inner surfaces of each container bottom to measure the thickness along the predetermined path on each container bottom. The wheel has a drive that provides a constant speed of rotation so the laser detector measures the container bottom thicknesses along the same path on each container. An actuator of the apparatus removes from the conveyor containers having thicknesses that are out of tolerance with respect to a design specification.
Blow molded container inspection apparatus as described above in accordance with the invention allows inspection of the thicknesses of up to 100 percent of a production run of containers.